Peer to Peer Mobile User Equipment Communication with On-Demand Discovery Signal Transmission

ABSTRACT

In some embodiments, a user equipment device (UE) implements a method for discovering the presence of neighboring UEs using an on-demand discovery signal transmission technique. This discovery process may be performed to enable the UEs to perform peer-to-peer communications with each other, wherein peer-to-peer communications is defined as direct communication between the UEs without involving a base station. The UE may be configured to transmit a discovery request signal when it has moved greater than a threshold amount since transmission of a prior discovery request signal. The discovery request signal causes one or more neighboring UEs to each transmit a discovery signal in response, and also causes the UE which generated the discovery request signal to transmit its own discovery signal. The received discovery signal from each of the neighboring UEs is useable to discover, or detect the presence of, these neighboring UEs.

PRIORITY CLAIM

The present application is a continuation of U.S. patent applicationSer. No. 14/870,763 titled “Peer to Peer Mobile User EquipmentCommunication with On-Demand Discovery Signal Transmission” filed onSep. 30, 2015, now U.S. Pat. No. 10/085,144, which claims benefit ofpriority of provisional application No. 62/059,078 titled “Peer to PeerMobile User Equipment Communication with On-Demand Discovery SignalTransmission” filed on Oct. 2, 2014, and which are both herebyincorporated by reference in their entirety as though fully andcompletely set forth herein.

The claims in the instant application are different than those of theparent application or other related applications. The Applicanttherefore rescinds any disclaimer of claim scope made in the parentapplication or any predecessor application in relation to the instantapplication. The Examiner is therefore advised that any such previousdisclaimer and the cited references that it was made to avoid, may needto be revisited. Further, any disclaimer made in the instant applicationshould not be read into or against the parent application or otherrelated applications.

FIELD

The present application relates to wireless cellular communication,including to methods for discovering neighboring User Equipment (UE)with reduced power requirements.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage. Further,wireless communication technology has evolved from voice-onlycommunications to also include the transmission of data, such asInternet and multimedia content. Therefore, improvements are desired inwireless communication. In particular, the large amount of functionalitypresent in a user equipment (UE), e.g., a wireless device such as acellular phone, can place a significant strain on the battery life ofthe UE.

One development in mobile device communications is peer-to-peercommunications, where one UE can discover the presence of a neighboringUE and communicate directly with the neighboring UE in a peer-to-peermanner, i.e., without involvement of a base station. In wirelessnetworks, the term “discovery” refers to the process of a UE finding ordiscovering neighboring UE's with which it can communicate. In currentsystems, UEs which use a broadcast based discovery mechanism areconstantly transmitting and listening for discovery signals to keeptheir neighbor status up to date, irrespective of the existence oflisteners/neighbors. This can waste the battery of the UE in situationswhere there is not much new information exchange among UEs.

Therefore, improvements in the field would be desirable.

SUMMARY

Embodiments are presented herein of, inter alia, a user equipment (UE)and associated method for discovering the presence of neighboring UEsusing an on-demand discovery signal transmission technique. Thisdiscovery process may be performed to enable the UEs to performpeer-to-peer communications with each other, wherein peer-to-peercommunications is defined as direct communication between the UEswithout involving a base station. A UE may comprise at least one antennafor performing wireless cellular communication, at least one radiocoupled to the antenna that performs cellular communication, and one ormore processors coupled to the radio.

The UE may be configured to transmit a discovery request signal over adiscovery request channel, which may be a shared discovery requestchannel. The discovery request channel may be at the beginning of adiscovery resource set (DRS), i.e., a set of contiguous discoveryresources or sub-frames. A UE may transmit a discovery request signal inresponse to determining that the UE has moved greater than a thresholdamount since transmission of a prior discovery request signal. In otherwords, a UE may not transmit a discovery request signal when the UE hasbeen stationary or has moved less than a threshold amount since its lasttransmission of a discovery request signal.

The UE may transmit the discovery request signal either when: 1) itdesires to broadcast its own discovery signal through its discoverychannel; or 2) when the UE desires to trigger its neighbor UEs to sendout their discovery request signals. The discovery request signal isconfigured to cause one or more neighboring UEs to each transmit adiscovery signal in response, and also causes the UE which generated thediscovery request signal to transmit its own discovery signal. In someembodiments, UEs may listen only for certain relevant discovery requestsignals and hence only broadcast their discovery signals in response todetection of a relevant discovery request signal.

In response to transmitting its discovery request signal, the UE mayreceive a discovery signal from each of the one or more neighboring UEs.The received discovery signal from each of the neighboring UEs isuseable to discover, or detect the presence of, these neighboring UEs.The discovery request signal may be transmitted in a discovery requestchannel that occurs in a first sub-frame of a discovery resource set,and discovery signals from each of the neighboring UEs may be receivedin subsequent sub-frames of the discovery resource set. If a UE does nothear or detect any relevant discovery request signals, the UE may sleepduring the remainder of the discovery resource set (DRS).

In one embodiment, UEs perform this discovery process to become aware ofthe presence of other neighboring UEs for the purpose of performingpeer-to-peer communication with neighboring UEs after discovery. Forexample, a software application executing on the UE may cause thediscovery process to occur, so that the software application candiscovery neighboring UEs for peer-to-peer communication. The discoveryrequest channel used by a UE may be determined based on the applicationtype (or application category) of the software application that iscurrently running on the UE and which is performing the discoveryprocess. For example, the discovery request channel may be selectedbased on one or more of an application type, an application ID, or anapplication user ID. In another embodiment, the discovery requestchannel may be selected based on a hash of an identifier (discoveryidentifier) of the software application. Alternatively, a hybridapproach may be used which uses both the application type and a hash ofthe application's discovery identifier.

Thus each UE may be configured to monitor one or more relevant discoveryrequest channels in a discovery resource set. Each UE may determinewhether any discovery request signals are received on the relevantdiscovery request channels which are relevant to the UE. Here therelevant discovery request channels being monitored, and the relevanceof discovery request signals detected, may be based on the applicationtype of the software application currently executing on the UE, or othercriteria. The UE may transmit a discovery signal on a discovery channelin the discovery resource set in response to detecting a relevantdiscovery request signal. Each respective UE's discovery signal isuseable by other UEs in discovering the presence of the respective UE. AUE is configured to sleep for a remainder of the discovery resource setin response to determining that no relevant discovery request signalshave been detected.

This Summary is intended to provide a brief overview of some of thesubject matter described in this document. Accordingly, it will beappreciated that the above-described features are merely examples andshould not be construed to narrow the scope or spirit of the subjectmatter described herein in any way. Other features, aspects, andadvantages of the subject matter described herein will become apparentfrom the following Detailed Description, Figures, and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present subject matter can be obtainedwhen the following detailed description of the embodiments is consideredin conjunction with the following drawings.

FIG. 1 illustrates an exemplary wireless communication system;

FIG. 2 illustrates an example base station (“BS”, or in the context ofLTE, an “eNodeB” or “eNB”) in communication with a wireless device;

FIG. 3 illustrates a block diagram for an example implementation of aUser Equipment (UE);

FIG. 4 illustrates a block diagram for an example embodiment of a basestation;

FIG. 5 illustrates an example of UEs broadcasting discovery signals todiscover neighboring UEs;

FIG. 6 illustrates the discovery resources in an example discoverychannel of a UE;

FIG. 7 illustrates a conventional method which increases the length ofthe wake-up period for discovery signal transmission;

FIG. 8 illustrates one embodiment of an example method for on demanddiscovery signal transmission;

FIG. 9 illustrates an example transmission and reception radius of a UElocality of the wake-up procedure;

FIG. 10 is a flowchart diagram illustrating example discovery channelassignment by the base station;

FIG. 11 is a flowchart diagram illustrating an example method for a UEdetermining a discovery request channel based on discovery information;

FIG. 12 is a flowchart diagram illustrating a UE performing an examplewake up and sleep operation;

FIG. 13 is an example graph illustrating the trade-off between thenumber of discovery request channels and reliability;

FIG. 14 illustrates an example embodiment where a single discoveryrequest channel is shared among all of the UEs, where each UE isassigned at least one discovery channel (DC);

FIG. 15 illustrates an example embodiment where a dedicated requestchannel is assigned to each discovery channel;

FIG. 16 illustrates an example embodiment involving multiple shareddiscovery request channels, where each discovery request channel isshared by one or more UEs who are assigned at least one DC;

FIG. 17 illustrates an example method of category-based mapping, wherediscovery signals from apps with the same category have the same requestchannel number;

FIG. 18 illustrates an example method of hash-based mapping, where eachUE or application in the UE that has at least one assigned discoveryrequest channel has a unique value called a discovery identifier (DI)which is used for information filtering by receive UEs;

FIG. 19 illustrates an example hybrid approach which involves bothcategory-based and hash-based mapping;

FIG. 20 illustrates an example of a physical design of discovery requestchannels; and

FIG. 21 illustrates an example of orthogonal discovery request channels.

While the features described herein are susceptible to variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the drawings and detaileddescription thereto are not intended to be limiting to the particularform disclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the subject matter as defined by the appended claims.

The term “configured to” is used herein to connote structure byindicating that the units/circuits/components include structure (e.g.,circuitry) that performs the task or tasks during operation. As such,the unit/circuit/component can be said to be configured to perform thetask even when the specified unit/circuit/component is not currentlyoperational (e.g., is not on). The units/circuits/components used withthe “configured to” language include hardware—for example, circuits,memory storing program instructions executable to implement theoperation, etc. Reciting that a unit/circuit/component is “configuredto” perform one or more tasks is expressly intended not to invoke 35U.S.C. § 112(f) for that unit/circuit/component.

DETAILED DESCRIPTION Terminology

The following is a glossary of terms used in this disclosure:

Memory Medium—Any of various types of non-transitory memory devices orstorage devices. The term “memory medium” is intended to include aninstallation medium, e.g., a CD-ROM, floppy disks, or tape device; acomputer system memory or random access memory such as DRAM, DDR RAM,SRAM, EDO RAM, Rambus RAM, etc.; a non-volatile memory such as a Flash,magnetic media, e.g., a hard drive, or optical storage; registers, orother similar types of memory elements, etc. The memory medium mayinclude other types of non-transitory memory as well or combinationsthereof. In addition, the memory medium may be located in a firstcomputer system in which the programs are executed, or may be located ina second different computer system which connects to the first computersystem over a network, such as the Internet. In the latter instance, thesecond computer system may provide program instructions to the firstcomputer for execution. The term “memory medium” may include two or morememory mediums which may reside in different locations, e.g., indifferent computer systems that are connected over a network. The memorymedium may store program instructions (e.g., embodied as computerprograms) that may be executed by one or more processors.

Carrier Medium—a memory medium as described above, as well as a physicaltransmission medium, such as a bus, network, and/or other physicaltransmission medium that conveys signals such as electrical,electromagnetic, or digital signals.

Programmable Hardware Element—includes various hardware devicescomprising multiple programmable function blocks connected via aprogrammable interconnect. Examples include FPGAs (Field ProgrammableGate Arrays), PLDs (Programmable Logic Devices), FPOAs (FieldProgrammable Object Arrays), and CPLDs (Complex PLDs). The programmablefunction blocks may range from fine grained (combinatorial logic or lookup tables) to coarse grained (arithmetic logic units or processorcores). A programmable hardware element may also be referred to as“reconfigurable logic”.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

User Equipment (UE) (or “UE Device”)—any of various types of computersystems devices which are mobile or portable and which performs wirelesscommunications. Examples of UE devices include mobile telephones orsmart phones (e.g., iPhone™, Android™-based phones), portable gamingdevices (e.g., Nintendo DS™, PlayStation Portable™, Gameboy Advance™,iPhone™), laptops, wearable devices (e.g. smart watch, smart glasses),PDAs, portable Internet devices, music players, data storage devices, orother handheld devices, etc. In general, the term “UE” or “UE device”can be broadly defined to encompass any electronic, computing, and/ortelecommunications device (or combination of devices) which is easilytransported by a user and capable of wireless communication.

Base Station—The term “Base Station” (also called “eNB”) has the fullbreadth of its ordinary meaning, and at least includes a wirelesscommunication station installed at a fixed location and used tocommunicate as part of a wireless telephone system or radio system.

Processing Element—refers to various elements or combinations ofelements that are capable of performing a function in a device, such asa user equipment or a cellular network device. Processing elements mayinclude, for example: processors and associated memory, portions orcircuits of individual processor cores, entire processor cores,processor arrays, circuits such as an ASIC (Application SpecificIntegrated Circuit), programmable hardware elements such as a fieldprogrammable gate array (FPGA), as well any of various combinations ofthe above.

Automatically—refers to an action or operation performed by a computersystem (e.g., software executed by the computer system) or device (e.g.,circuitry, programmable hardware elements, ASICs, etc.), without userinput directly specifying or performing the action or operation. Thusthe term “automatically” is in contrast to an operation being manuallyperformed or specified by the user, where the user provides input todirectly perform the operation. An automatic procedure may be initiatedby input provided by the user, but the subsequent actions that areperformed “automatically” are not specified by the user, i.e., are notperformed “manually”, where the user specifies each action to perform.For example, a user filling out an electronic form by selecting eachfield and providing input specifying information (e.g., by typinginformation, selecting check boxes, radio selections, etc.) is fillingout the form manually, even though the computer system must update theform in response to the user actions. The form may be automaticallyfilled out by the computer system where the computer system (e.g.,software executing on the computer system) analyzes the fields of theform and fills in the form without any user input specifying the answersto the fields. As indicated above, the user may invoke the automaticfilling of the form, but is not involved in the actual filling of theform (e.g., the user is not manually specifying answers to fields butrather they are being automatically completed). The presentspecification provides various examples of operations beingautomatically performed in response to actions the user has taken.

FIG. 1—Wireless Communication System

FIG. 1 illustrates one embodiment of a wireless cellular communicationsystem. It is noted that FIG. 1 represents one possibility among many,and that features of the present disclosure may be implemented in any ofvarious systems, as desired.

As shown, the exemplary wireless communication system includes a basestation 102A which communicates over a transmission medium with one ormore wireless devices 106A, 106B, etc., through 106N. Wireless devicesmay be user devices, which may be referred to herein as “user equipment”(UE) or UE devices.

The base station 102 may be a base transceiver station (BTS) or cellsite, and may include hardware that enables wireless communication withthe UE devices 106A through 106N. The base station 102 may also beequipped to communicate with a network 100 (e.g., a core network of acellular service provider, a telecommunication network such as a publicswitched telephone network (PSTN), and/or the Internet, among variouspossibilities). Thus, the base station 102 may facilitate communicationbetween the UE devices 106 and/or between the UE devices 106 and thenetwork 100.

The communication area (or coverage area) of the base station 102 may bereferred to as a “cell.” The base station 102 and the UEs 106 may beconfigured to communicate over the transmission medium using any ofvarious radio access technologies (RATs) or wireless communicationtechnologies, such as GSM, UMTS (WCDMA, TDS-CDMA), LTE, LTE-Advanced(LTE-A), HSPA, 3GPP2 CDMA2000 (e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD),Wi-Fi, WiMAX etc.

Base station 102 and other similar base stations (not shown) operatingaccording to one or more cellular communication technologies may thus beprovided as a network of cells, which may provide continuous or nearlycontinuous overlapping service to UE devices 106A-N and similar devicesover a wide geographic area via one or more cellular communicationtechnologies.

Thus, while base station 102 may presently represent a “serving cell”for wireless devices 106A-N as illustrated in FIG. 1, each UE device 106may also be capable of receiving signals from one or more other cells(e.g., cells provided by other base stations), which may be referred toas “neighboring cells”. Such cells may also be capable of facilitatingcommunication between user devices and/or between user devices and thenetwork 100.

Note that at least in some instances a UE device 106 may be capable ofcommunicating using multiple wireless communication technologies. Forexample, a UE device 106 might be configured to communicate using two ormore of GSM, UMTS, CDMA2000, WiMAX, LTE, LTE-A, WLAN, Bluetooth, one ormore global navigational satellite systems (GNSS, e.g., GPS or GLONASS),one and/or more mobile television broadcasting standards (e.g., ATSC-M/Hor DVB-H), etc. Other combinations of wireless communicationtechnologies (including more than two wireless communicationtechnologies) are also possible. Likewise, in some instances a UE device106 may be configured to communicate using only a single wirelesscommunication technology.

FIG. 2 illustrates UE device 106 (e.g., one of the devices 106A through106N) in communication with base station 102. The UE device 106 may havecellular communication capability, and as described above, may be adevice such as a mobile phone, a hand-held device, a media player, acomputer, a laptop or a tablet, or virtually any type of wirelessdevice.

The UE device 106 may include a processing element, such as a processorthat is configured to execute program instructions stored in memory. TheUE device 106 may perform any of the method embodiments described hereinby executing such stored instructions. Alternatively, or in addition,the UE device 106 may include a programmable hardware element such as anFPGA (field-programmable gate array), or other circuitry, that isconfigured to perform any of the method embodiments described herein, orany portion of any of the method embodiments described herein.

In some embodiments, the UE device 106 may be configured to communicateusing any of multiple radio access technologies and/or wirelesscommunication protocols. For example, the UE device 106 may beconfigured to communicate using one or more of GSM, UMTS, CDMA2000, LTE,LTE-A, WLAN, Wi-Fi, WiMAX or GNSS. Other combinations of wirelesscommunication technologies are also possible.

The UE device 106 may include one or more antennas for communicatingusing one or more wireless communication protocols or technologies. Inone embodiment, the UE device 106 might be configured to communicateusing a single shared radio. The shared radio may couple to a singleantenna, or may couple to multiple antennas (e.g., for MIMO) forperforming wireless communications. Alternatively, the UE device 106 mayinclude two or more radios. For example, the UE 106 might include ashared radio for communicating using either of LTE or 1×RTT (or LTE orGSM), and separate radios for communicating using each of Wi-Fi andBluetooth. Other configurations are also possible.

FIG. 3—Example Block Diagram of a UE

FIG. 3 illustrates one possible block diagram of a UE 106. As shown, theUE 106 may include a system on chip (SOC) 300, which may includeportions for various purposes. For example, as shown, the SOC 300 mayinclude processor(s) 302 which may execute program instructions for theUE 106, and display circuitry 304 which may perform graphics processingand provide display signals to the display 340. The processor(s) 302 mayalso be coupled to memory management unit (MMU) 340, which may beconfigured to receive addresses from the processor(s) 302 and translatethose addresses to locations in memory (e.g., memory 306, read onlymemory (ROM) 350, NAND flash memory 310). The MMU 340 may be configuredto perform memory protection and page table translation or set up. Insome embodiments, the MMU 340 may be included as a portion of theprocessor(s) 302.

The UE 106 may also include other circuits or devices, such as thedisplay circuitry 304, radio 330, connector I/F 320, and/or display 340.

In the embodiment shown, ROM 350 may include a bootloader, which may beexecuted by the processor(s) 302 during boot up or initialization. Asalso shown, the SOC 300 may be coupled to various other circuits of theUE 106. For example, the UE 106 may include various types of memory(e.g., including Flash 310), a connector interface 320 (e.g., forcoupling to a computer system), the display 340, and wirelesscommunication circuitry (e.g., for communication using LTE, CDMA2000,Bluetooth, WiFi, GPS, etc.).

The UE device 106 may include at least one antenna, and in someembodiments multiple antennas, for performing wireless communicationwith base stations and/or other devices. For example, the UE device 106may use antenna 335 to perform the wireless communication. As notedabove, the UE may in some embodiments be configured to communicatewirelessly using a plurality of wireless communication standards.

As described herein, the UE 106 may include hardware and softwarecomponents for implementing discovery methods according to embodimentsof this disclosure.

The processing element (e.g., processor) 302 of the UE device 106 may beconfigured to implement part or all of the methods described herein,e.g., by executing program instructions stored on a memory medium (e.g.,a non-transitory computer-readable memory medium). In other embodiments,processing element may be configured as a programmable hardware element,such as an FPGA (Field Programmable Gate Array), or as an ASIC(Application Specific Integrated Circuit).

FIG. 4—Example Block Diagram of a Base Station

FIG. 4 illustrates one embodiment of a base station 102. It is notedthat the base station of FIG. 4 is merely one example of a possible basestation. As shown, the base station 102 may include processor(s) 404which may execute program instructions for the base station 102. Theprocessor(s) 404 may also be coupled to memory management unit (MMU)440, which may be configured to receive addresses from the processor(s)404 and translate those addresses to locations in memory (e.g., memory460 and read only memory (ROM) 450) or to other circuits or devices.

The base station 102 may include at least one network port 470. Thenetwork port 470 may be configured to couple to a telephone network andprovide a plurality of devices, such as UE devices 106, access to thetelephone network as described above.

The network port 470 (or an additional network port) may also oralternatively be configured to couple to a cellular network, e.g., acore network of a cellular service provider. The core network mayprovide mobility related services and/or other services to a pluralityof devices, such as UE devices 106. In some cases, the network port 470may couple to a telephone network via the core network, and/or the corenetwork may provide a telephone network (e.g., among other UE devicesserviced by the cellular service provider).

The base station 102 may include a radio 430, a communication chain 432and at least one antenna 434. The base station may be configured tooperate as a wireless transceiver and may be further configured tocommunicate with UE devices 106 via radio 430, communication chain 432and the at least one antenna 434. Communication chain 432 may be areceive chain, a transmit chain or both. The radio 430 may be configuredto communicate via various RATs, including, but not limited to, GSM,UMTS, LTE, WCDMA, CDMA2000, WiMAX, etc.

The processor(s) 404 of the base station 102 may be configured toimplement part or all of the methods described herein, e.g., byexecuting program instructions stored on a memory medium (e.g., anon-transitory computer-readable memory medium). Alternatively, theprocessor 404 may be configured as a programmable hardware element, suchas an FPGA (Field Programmable Gate Array), or as an ASIC (ApplicationSpecific Integrated Circuit), or a combination thereof.

As described above, in some embodiments a UE is able to directlycommunicate with a neighboring UE in a peer-to-peer fashion, i.e., theUE's are able to communicate directly with each other without thecommunications being required to pass through a base station. For UEswhich are configured to perform peer-to-peer communication, these UEsmay use a discovery mechanism that is based on broadcasting signals toneighboring UEs. In other words, a first UE may broadcast a signal thatmay be received by neighboring UEs, thus alerting the neighboring UEs tothe presence of the first UE. In a similar manner, each of the UEs maybroadcast a signal to alert neighboring UEs of its presence.

One issue that arises is that UEs may keep sending and listening fordiscovery signals to keep their neighbor status (their information onneighboring UEs) up to date, irrespective of the existence oflistening/neighboring UEs, or changes in the presence oflisteners/neighbors. This could result in a waste of battery usage whenthere is little or no new information exchange among UEs.

Therefore, one embodiment of this disclosure relates to an on-demandapproach based on request and responses. This on-demand approach may bemore energy efficient than conventional methods. More specifically, oneembodiment of the method relates to request-based discovery signaltransmission, wherein the UE may send out a discovery signal only whenthere is a request from any of its neighbors. A second embodimentrelates to category-based discovery request channels, wherein therequest may be categorized and transmitted through shared category-basedrequest channels to reduce unnecessary or spurious discovery signaltransmission.

FIG. 5—Current Discovery Method

FIG. 5 illustrates a conventional method for performing discovery ofneighboring UEs in a wireless network. In wireless networks, discoveryis the process of finding neighboring nodes or UEs, e.g., for thepurpose of enabling peer-to-peer communication between the UEs. Asshown, UE1 and UE2 periodically broadcast discovery signals though theirrespective discovery resource. UE1 discovers UE2 if it receives thebroadcasting discovery signal from UE2. In a similar manner, UE2discovers UE1 if UE2 receives the broadcasting discovery signal fromUE1. These signals may be transmitted through orthogonal resources toavoid collisions and hence help ensure successful reception. As shown,the broadcast period is the time period between a respective UE'sbroadcast of a discovery signal.

FIG. 6—Resources Used for Discovery

FIG. 6 illustrates an example of resources used for discoverycommunication according to one embodiment. The embodiment shown in FIG.6 assumes half duplex communication. Here the basic transmission timeunit is a sub-frame, and the top of FIG. 6 shows a sequence ofsub-frames in the time domain, where each rectangle in the sequencecorresponds to a sub-frame. Each of the shaded portions of the sequenceis a set of Discovery Resources, i.e., a Discovery Resource Set (DRS).As shown, a set of discovery resources comprises a set of sub-frames inthe larger sequence of sub-frames.

Each respective DRS is broken out and shown in greater detail in FIG. 6in the square below. The square shows a 2-D grid of boxes where each boxrepresents a Discovery Resource (DR) in the DRS. For the 2-D grid ofDRs, the horizontal axis is time and the vertical axis is frequency.Thus, as shown, each DRS comprises a set of Discovery Resources (DRs),where each Discovery Resource (DR) is a set of time-frequency resourcesreserved to send a discovery signal from one UE to others. An example oftime-frequency resources is, e.g., one or more RBs (resource blocks) inLTE. A Discovery Resource Set (DRS) is thus a set of neighboring DRs,i.e., a set of neighboring sub-frames that are allocated for the purposeof discovery resources.

A Discovery Channel (DC) is a logical channel which is mapped to onerespective DR in each DRS. Thus the box in the lower left of FIG. 6illustrates a Discovery Resource Set comprising a number of DiscoveryResources, where the number inside each box indicates a correspondingDiscovery Channel number. In conventional systems, each UE in thediscovery process keeps sending out its discovery signal through itsassigned discovery channel regardless of the presence or status ofneighboring UEs. This results in waste of power and reduced batterylife.

In one embodiment UEs may perform a periodic wake-up to engage in thediscovery process. In other words, a UE periodically wakes up to eithersend a discovery request signal, monitor discovery channel(s) for otherdiscovery request signals, or monitor discovery signals transmitted byother UEs, and also sends its own discovery signal when requested to doso. A periodic wake-up for discovery results in fast batteryconsumption, which eventually could reduce device standby timesignificantly.

In a stationary network where UEs are stationary or moving very slowly,it is likely that UEs in the network continue receiving the samediscovery information over and over. In this type of scenario, a UEsending the same discovery information to the same set of neighbors andreceiving the same discovery information from them would waste batterypower without exchange of new information among UEs. Thus in suchstationary networks, sending or receiving a discovery signal less oftencan save battery power.

FIG. 7—Increased Wake-Up Period

FIG. 7 illustrates one approach for reducing power consumption, wherethis approach involves increasing the wake-up period between instancesof the discovery process. The top of FIG. 7 shows a time sequence ofsub-frames, with each shaded portion allocated for a set of DiscoveryResources, i.e., a Discovery Resource Set (DRS). With the increase ofwake-up period, the discovery resource sets (DRS's) are spaced fartherapart in time, and hence each of the UEs wakes up less often, and thuseach can save battery power. However, this is achieved at the expense ofincreased discovery delay (since inter wake-up time is larger).Furthermore, heretofore it has not been possible to dynamically adjustthe length of the wake-up period depending on the number of UEs in thenetwork or the mobility of UEs in the network. Thus improvements in thefield are desired.

One embodiment described herein relates to a demand-based discoveryprocess which results in reduced power consumption. As one example, a UEmay send out discovery request signal through a shared discovery requestchannel in the following two cases:

1) when the UE wants to send its own discovery signal through itsdiscovery channel, and/or

2) when the UE wants to trigger its neighbors to send out theirdiscovery signals.

UEs not sending a discovery request signal should listen to the variousdiscovery request channels. For the respective UEs listening on thediscovery request channels, in response to receipt of any relevantdiscovery request signal, each respective UE should broadcast its owndiscovery signal in response thereto. Thus, when a first UE broadcasts adiscovery request signal, the neighboring UEs that receive the discoveryrequest signal respond with their respective discovery signals. When UEsdo not hear any discovery request signals on a respective discoveryrequest channel, i.e., when no discovery request signal is transmittedon a respective discovery request channel for a DRS, the UEs may sleepduring this discovery process, i.e., may sleep during this DRS.

FIG. 8—Example of the Demand-Based Discovery Process

FIG. 8 illustrates an example of the demand-based discovery processaccording to one embodiment. The top of FIG. 8 shows a time sequence ofsub-frames, with this illustrated sequence of sub-frames having twodifferent discovery resource sets (DRS's). Each DRS is illustrated ashatched portions corresponding to a set of discovery resources (DRs),i.e., sub-frames that are allocated as DRs, or as a DRS. The first DR ineach set, which is shown with a fully hatched shading, is a sub-framereserved for a discovery request channel. The remaining DRs of the DRS,which have diagonal hatching in only one direction, are sub-frames thatare reserved for transmit/receive of a discovery signal by respectiveUEs, in response to a discovery request signal. FIG. 8 also illustratesthe Discovery Resource (DR) period between respective Discovery ResourceSets (DRSs).

Below this sequence of sub-frames, FIG. 8 illustrates operation of UE1and UE2. Here presume that UE1 and UE2 each has its own discoveryresource and discovery request channel assigned by the eNB. Theoperations of UE1 and UE2 at times t1-t4 are as follows:

t1: UE1 sends out a discovery request signal on the discovery requestchannel to trigger its neighbors to broadcast. The discovery requestchannel is the first sub-frame of the DRS, and this transmission isshown with horizontally and vertically hatched shading.

t1: UE2 listens to the discovery request signal from UE1 on thediscovery request channel.

t2: UE2 sends out its own discovery signal, on its assigned discoveryresource, in response to the discovery request signal.

t3: UE1 also sends out its discovery signal for its neighbors.

t4: Both UE1 and UE2 listen on the discovery request channel of the nextDRS. There is no discovery request signal that is transmitted on thediscovery request channel of this next DRS, and thus UE1 and UE2 sleepduring the DRS.

FIG. 9—Locality of Wake-Up

FIG. 9 illustrates locality of the wake-up that is performed. In oneembodiment, a UE wakes up only when it detects a discovery requestsignal from one or more of its neighbors. Thus if the UE does not haveany neighbors, then there is no discovery signal transmission thatoccurs. In one embodiment, a first UE is considered to have a neighborwhen there is another UE that is within the first UE's transmission andreception radius. Thus a respective UE is a neighboring UE of a first UEif the respective UE is within the transmission/reception radius of thefirst UE.

Consider the example of FIG. 9 and assume UE1 and UE3 are the neighborsof UE2, and UE2 and UE4 are the neighbors of UE3. If UE2 sends adiscovery request signal, only UE1 and UE3 are capable of listening toor detecting the request. In response to UE2 transmitting the discoveryrequest signal, UE1, UE2, and UE3 wake up and transmit their discoverysignal during the DRS. UE4 sleeps during the DRS since it did notreceive the discovery request signal from UE2.

FIG. 10—Explicit Assignment of Discovery Channel by Base Station

FIG. 10 is a flowchart diagram illustrating one embodiment of a methodfor assignment of a discovery channel to a UE by a base station.

At 1000 the UE requests one or more discovery channels from the eNB(base station). At 1000 the UE may be executing a software applicationthat utilizes or requires peer-to-peer communication with other UEs.Examples of such software applications include geocaching or geotaggingapplications, game applications which utilize lots of communicationbetween neighboring UEs participating in the respective game, socialmedia applications which perform communications based on geographicproximity, messenger applications, advertising applications whichprovide advertising based on geographic proximity, file transferapplications, accessory or utility applications, and any of variousother types of apps which may utilize peer-to-peer communicationsbetween neighboring UEs. Thus this software application executing on theUE may request various discovery channels or resources to use inperforming discovery of neighboring UEs. This request may take the formof a control signaling from the UE to the eNB. In making the request fordiscovery channels, the UE may send any relevant information such asapplication category, or hash value, or any random value, or other typesof information.

At 1002 the base station assigns one or more discovery channels to theUE, e.g., for use by the software application executing on the UE. Thebase station may assign discovery channels to the UE through a RadioResource Control (RRC) message or other types of control signaling. Herethe base station may assign a particular discovery resource in adiscovery resource set to the UE (or to the app executing on the UE) touse for transmission of its discovery signal.

At 1004 the base station assigns one or more associated discoveryrequest channels to the UE (or to the app executing on the UE). The basestation may assign one or more associated discovery request channels tothe UE based on information that the UE has provided, such as theapplication type (or application category) of the software application,a hash value of a unique identifier (discovery identifier) associatedwith the software application, or a random number. The hash value or arandom number may be used to assign a discovery request channel, suchthat the pool of discovery request channels are assigned in a moreuniform manner, i.e., to prevent overuse of certain channels andunder-use of others. Hash-based mapping is discussed in more detailbelow.

The method of FIG. 10 may be performed for each of one or more of, or aplurality of, software applications executing on a respective UE.

FIG. 11—UE Determines Discovery Request Channel Based on DiscoveryInformation

FIG. 11 is a flowchart diagram illustrating another embodiment of amethod whereby a UE requests one or more discovery request channels froma base station. In this embodiment, the UE may determine the discoveryrequest channels it should use based at least in part on certaininformation associated with the UE or applications executing on the UE.

At 1100 the UE requests one or more discovery channels from the eNB(base station). This step may be similar to, or the same as, 1000 ofFIG. 10, discussed above.

At 1102 the base station assigns one or more discovery channels to theUE. This step is the same as 1002 of FIG. 10, discussed above.

At 1104 the UE determines its associated discovery request channel(s)based at least in part on relevant information (e.g., applicationcategory, App ID, App User ID, device ID, random number, hash function,etc.). It is noted that some or all of this information may be signaledby the UE. For example, assume a first software application is executingon the UE which performs the method of FIG. 11. When the UE receivesdiscovery request channel assignment information from the base stationat 1102, at 1014 the UE may use information related to the firstsoftware application, such as its application category (applicationtype), application ID, and/or application user ID, to determine theappropriate discovery request channels to be assigned. As noted above, ahash function or random number methodology may also, or instead, be usedto help ensure that discovery request channel assignments are spreadevenly among the available discovery request channels.

FIG. 12—Wake-Up and Sleep Operation

FIG. 12 is a flowchart diagram illustrating a method for wake-up andsleep operation according to one embodiment. The method of FIG. 12 maybe performed by each UE, e.g., by each of a plural subset of UEs in aneighborhood. Here it is presumed that a respective UE is executing asoftware application that employs some form of peer-to-peercommunication, and in addition the software application uses a discoveryprocedure as described herein to enable the respective UE to discover,or be aware of the presence of, other UEs in its neighborhood. Thediscovery procedure may enable the respective UE to discover other UEsthat are executing a similar software application. Thus, for example, ina respective geographic area, in one embodiment only UEs that areexecuting a certain software application may participate in thediscovery methods described herein. In other embodiments, all UEs in acertain geographic area may execute the methods described herein,regardless of what software applications they are currently executing.

As shown, at 1200 every time a discovery request channel sub-frameoccurs, the method, e.g., a first UE, may perform the followingoperations. As noted above, a discovery request channel may occur at thebeginning of a discovery resource set (DRS), e.g., as the firstsub-frame of a DRS.

At 1202 the UE determines if it wants to transmit a discovery signalduring the DRS. This determination may be based on whether the UE hasmoved greater than a threshold amount since the last time it transmittedits discovery signal. This movement threshold amount may any of variouspredetermined distances of movement since the last discoverytransmission, such as 100/200/500 meters. For example, if the UE hasbeen relatively stationary since the last time it transmitted itsdiscovery signal, then the UE likely will not transmit its discoveryrequest signal. In this instance, other UEs that previously receivedthis UE's last discovery signal, and which have not since moved away,will already be aware of this UE's presence. It is also presumed thatnew UEs entering the neighborhood of this UE will have sent a discoveryrequest signal due to their movement, causing this UE to have previouslyresponded with its discovery signal.

If the UE determines that it does want to transmit its discovery signalat 1202, then at 1204 the UE transmits a discovery request signalthrough its associated discovery request channel in the respective DRS.This discovery request signal causes the UE to transmit its owndiscovery signal in its assigned discovery channel in the DRS. Thisdiscovery request signal also acts as a trigger that causes other UEs inits neighborhood to respond with their discovery signals.

At 1206 the UE wakes up during the DRS. Here the UE wakes up during theDRS because it transmitted its discovery request signal in 1204. Inother words, because the UE has transmitted its discovery request signalin 1204, it wakes up during the DRS at 1206.

At 1208 the UE transmits its discovery signal through its discoverychannel. This discovery signal can be detected by other UEs in theneighborhood of this UE, thus enabling these other UEs to discover, ordetect the presence of, this UE. At 1208 the UE also listens for ormonitors the transmission of other discovery signals during the time inthe DRS when the UE is not broadcasting its own discovery signal. Inother words, the UE monitors other discovery channels in the DRS, i.e.,listens in on other discovery resource sub-frames in the DRS, to detectother UEs in its neighborhood that are transmitting their discoverysignals based on the UE's transmission of its discovery request signalin 1204.

If the UE determines that it does not want to transmit its discoverysignal at 1202, then at 1210 the UE monitors or listens for discoveryrequest signals on various of the discovery request channels. In oneembodiment, the UE listens for discovery request signals on all possiblediscovery request channels. In another embodiment, if a certain softwareapplication (of a certain application type or category) is executing onthe UE which performs this discovery method, then this softwareapplication may only listen to a subset of the discovery requestchannels associated with the same or similar application type as that ofthe software application executing on the UE.

At 1212 the UE determines if there is any discovery request signaldetected or received which is relevant to this UE. For example, the UEmay determine if there is any detected discovery request signal that hasthe same application type as that of the application which is currentlyexecuting on the UE, and which is controlling or implementing thediscovery process.

If at 1212 the UE determines that there is a discovery request signaldetected or received which is relevant to this UE, then operationproceeds to 1206, and steps 1206 and 1208 are executed as describedabove. Here the UE will wake up during the DRS in 1206 and at 1208 willboth transmit its discovery signal through its assigned discoverychannel and will also monitor and detect discovery signals transmittedby other UEs. Thus the UE will be able to discover the presence of otherUEs in its neighborhood that are broadcasting their discovery signals.

If at 1212 the UE determines that there is not a discovery requestsignal detected or received which is relevant to this UE, then at 1214the UE sleeps during the DRS, thus saving power.

FIG. 13—Design of Discovery Request Channels

One objective in the design of discovery request channels is to designreliable request channel(s) that may reduce power consumption of the UE.In order to achieve reduced power consumption, in one embodiment a firstUE may wake up only when any neighboring UE indicates that it wants tolisten to the first UEs' discovery signal. As shown in FIG. 13, indesigning the discovery channels, various metrics were considered, suchas reliability and power consumption. Reliability may be measured byfalse alarm (FA)/miss detection (MD) probability. FA/MD could be causedby multi-path fading, Doppler, noise, interference, etc. Powerconsumption may be measured by the number of spurious transmissions (orunnecessary discovery signal transmissions). Spurious transmissionoccurs when a UE sends a discovery signal transmission that is not usedby any of the UE's neighbors. The design of the discovery requestchannels may take into account the trade-off between the number ofchannels vs. reliability.

FIG. 14 shows Option 1 with a single shared discovery request channel.In this implementation, one single discovery request channel is sharedamong all the UEs, where each of the UEs is assigned at least onediscovery channel for responding to a discovery request. Thisimplementation has the benefit of high reliability. However, some of thenegatives are that if there is at least one UE transmitting on theshared discovery request channel, then this one UE wakes up all the UEsin its neighborhood and requires them to transmit on their respectivediscovery channels. However, many of these UEs in the neighborhood maynot be of interest to this UE, resulting in spurious transmission. Also,there is not much opportunity for power saving. Thus, as shown in FIG.13, with Option 1 using a single shared request channel there is a lowprobability of false alarm but also a larger number of spurioustransmission signals and a higher power consumption.

FIG. 15 shows Option 2 with a dedicated discovery request channel foreach UE. In FIG. 15 the shaded boxes on the left correspond tosub-frames reserved for discovery request channels. In thisimplementation, the system (e.g., the base station) assigns onededicated discovery request channel for each discovery channel, andhence for each UE. This implementation has the benefit of no collisionsamong request signals, since there is a dedicated request channel foreach discovery channel and thus each UE. However, this implementationrequires a large number of orthogonal request channels, which inconjunction with effects such as multi-path fading, Doppler, noise,interference, etc., can result in low reliability of the dedicatedrequest channels. Another drawback of Option 2 is that use of dedicateddiscovery channels may entail the use of a one bit indicator for eachchannel, which does not provide information about what discoveryinformation will be transmitted. Thus, since a UE is only receiving onebit (“yes” or “no”), a UE should have prior knowledge about itsneighbors, such as discovery channel numbers of UEs of interest or someform of IDs which could be mapped to discovery channels. Thus, withOption 2 using a dedicated request channel for each UE, there is ahigher probability of false alarm but also a smaller number of spurioustransmission signals and a lower power consumption.

FIG. 16 shows Option 3 with multiple shared request channels. In FIG. 16the shaded boxes on the left correspond to sub-frames reserved fordiscovery request channels. In Option 3 each discovery request channelmay be shared by one or more, and typically two or more, UEs, whereineach of the UEs is assigned at least one discovery channel. Thus Option3 uses multiple shared request channels, i.e., more than a single sharedrequest channel but not a dedicated request channel for each UE. Forexample, assume M is the number of discovery request channels and N isthe number of discovery resources, then M<N. Thus as shown in FIG. 13Option 3 makes a trade-off between power consumption and the number ofspurious transmission signals on the one hand vs. reliability of thediscovery channel, e.g., the number of false alarms and mis-detections,on the other hand. Various methods may be used for mapping discoverychannels to discovery request channels.

FIG. 17—Application Type Based Request Channel Mapping

FIG. 17 illustrates an example of category-based (applicationtype-based) mapping according to one embodiment. In FIG. 17 each of therectangular boxes represents a sub-frame reserved for discovery requestchannels. In this embodiment, all of the discovery signals fromapplications (apps) of the same category (same application type) utilizethe same discovery request channel number. FIG. 17 illustrates anexample where game applications use request channel number 1, socialnetworking applications use request channel number 2, messengerapplications use request channel number 3, advertising applications userequest channel number 4, accessory applications use request channelnumber 5, file transfer applications use request channel number 6, etc.It is noted that some request channels may be more popular than others,resulting in an uneven or non-uniform usage (and hence possiblyinefficient usage) of the request channel numbers. A benefit of thiscategory based mapping is the UEs may only be required to wake up whenapplication types in which the UE is interested are scheduled to betransmitted. A drawback of this category based mapping is that if a UEis configured to listen to a very popular category (application type),e.g., due to the type of application currently running on the UE, thenthere is very little opportunity for power saving.

FIG. 18—Hash Based Mapping

FIG. 18 illustrates an example of hash-based mapping according to oneembodiment. In FIG. 18 each of the rectangular boxes represents asub-frame reserved for discovery request channels. In this embodiment,each UE, or each application in the UE, which has at least one DRassigned has a unique value called discovery identifier (DI) which isused for information filtering by receive UEs. The discovery identifier(DI) may take the form of other types of values. For example, one ormore values such as application ID, user ID, application type (orcategory), etc. may be used instead of a DI

The DI is hashed to one value m of the request channel numbers 1, . . ., M, where:

-   -   m-Hash(DI₁, DI₂, . . . ) with 1<m<M; and    -   DI₁, DI₂, . . . are mapped to discovery request channel m.

In hash based mapping all of the discovery request channels are equallypopular. One benefit of hash-based mapping is that spurious transmissionrate becomes proportional to the total number of UEs transmitting. Onedrawback of hash-based mapping is that spurious transmission increasesas the total number of UEs transmitting discovery signals increases.

FIG. 19—Hybrid Type and Hash Based Mapping

FIG. 19 illustrates an example of a hybrid form of mapping using acombination of category based (application type based) mapping andhash-based mapping according to one embodiment. In FIG. 19 each of therectangular boxes represents a sub-frame reserved for discovery requestchannels.

In this embodiment both category and hash-based mapping are used, andeach discovery request channel is identified by application category andhash value. The “category” is determined by application type and the“hash value” is determined by DI (or other values as described above).In this implementation, the number of discovery request channels foreach category may depend on the popularity of the category. For example,a non-popular category may have only one assigned request channel (or asingle hash value). A popular category may have two or more assignedrequest channels. One benefit of this hybrid-based mapping is thatspurious transmissions are further reduced. One drawback of thishybrid-based mapping is that more request channels are required, whichcould reduce the reliability of an individual request channel. Also, itis not possible to completely remove spurious transmissions.

FIG. 20—Physical Design of Discovery Request Channels

FIG. 20 illustrates an example of the physical design of discoveryrequest channels. FIG. 20 illustrates a plurality of sub-frames, wherethe shaded portions represent discovery request channels. The designobjectives for discovery request channels may be to have a large numberof channels with a sufficiently high reliability. These discoveryrequest channels may exist in both the time and frequency domains. Inimplementations where a shared channel is used, multiple UEs having thesame (category, hash value) could send the same discovery request signalthrough the same channel. In one embodiment, the discovery requestchannels are distributed in the frequency domain for diversity. Eachchannel may be composed of a set of resource elements (REs) which isdistributed over the entire time frequency resource.

FIG. 21 illustrates the use of orthogonal request channels. As oneexample, this embodiment may use a Zadoff Chu sequence in the frequencydomain and a Walsh Hadamard sequence in the time domain. With thisscheme, it is possible to create multiple orthogonal channels in a giventime-frequency resource (e.g., one resource block). The total number ofchannels multiplexed though one time frequency resource block may beK*L, where K is the number of cyclic shifts in the ZC sequence, and L isthe number of orthogonal Walsh sequences.

Embodiments of the present disclosure may be realized in any of variousforms. For example some embodiments may be realized as acomputer-implemented method, a computer-readable memory medium, or acomputer system. Other embodiments may be realized using one or morecustom-designed hardware devices such as ASICs. Still other embodimentsmay be realized using one or more programmable hardware elements such asFPGAs.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of a methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a device (e.g., a UE 106) may be configured toinclude a processing element, e.g., a processor or a set of processorsand a memory medium, where the memory medium stores programinstructions, where the processor is configured to read and execute theprogram instructions from the memory medium, where the programinstructions are executable to implement a method, e.g., any of thevarious method embodiments described herein (or, any combination of themethod embodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets). Thedevice may be realized in any of various forms.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

What is claimed is:
 1. A wireless device, comprising: at least oneantenna; at least one radio communicatively coupled to the at least oneantenna, wherein the at least one radio is configured to performcellular communication using at least one radio access technology (RAT);one or more processors communicatively coupled to the at least oneradio, wherein the one or more processors and the at least one radio areconfigured to perform wireless voice and/or data communications usingthe at least one antenna; wherein the one or more processors and atleast one radio are configured to cause the wireless device to: monitorone or more discovery request channels in a discovery resource setassigned by a base station; determine that the wireless device has movedgreater than a threshold distance since transmission of a priordiscovery request signal to neighboring wireless devices, wherein thethreshold distance comprises a specified distance since the transmissionof the prior discovery request signal to the neighboring wirelessdevices; and transmit, in response to one of determining that adiscovery request signal relevant to the wireless device has beenreceived from a neighboring wireless device and determining that thewireless device has moved greater than a threshold distance sincetransmission of the prior discovery request signal, a discovery signalon a discovery request channel in the discovery resource set.
 2. Thewireless device of claim 1, wherein the one or more processors and atleast one radio are further configured to cause the wireless device to:perform peer-to-peer communication with the neighboring wireless deviceafter discovering the neighboring wireless device using the receiveddiscovery request signal.
 3. The wireless device of claim 1, wherein theone or more processors and at least one radio are further configured tocause the wireless device to: determine that the wireless device hasmoved less than the threshold amount since transmission of the priordiscovery request signal; and not transmit the discovery request signalin response to determining that the wireless device has moved less thanthe threshold amount since the transmission of the prior discoveryrequest signal.
 4. The wireless device of claim 1, wherein the discoveryrequest channel occurs in a first sub-frame of a discovery resource set.5. The wireless device of claim 1, wherein the wireless device furthercomprises a memory which stores a software application that isexecutable by the one or more processors; wherein transmission of thediscovery signal on the discovery request channel is performed by thesoftware application.
 6. The wireless device of claim 1, wherein the oneor more processors and the at least one radio are further configured tocause the wireless device to: request one or more discovery requestchannels from the base station.
 7. The wireless device of claim 1,wherein the discovery request channel is assigned to the UE by the basestation.
 8. An apparatus, comprising: a memory; and a processor incommunication with the memory, wherein the processor is configured to:generate instructions to transmit, in response to determining movementgreater than a threshold distance since transmission of a priordiscovery request signal to neighboring wireless devices, a discoveryrequest signal over a discovery request channel to the neighboringwireless devices, wherein the threshold distance is a specified distancesince the transmission of the prior discovery request signal; andreceive, over at least one of one or more discovery channels assigned bya base station, discovery signals from one or more of the neighboringwireless devices in response to transmission of the discovery requestsignal, wherein the received discovery signals are useable to discoverone or more of the neighboring wireless devices.
 9. The apparatus ofclaim 8, wherein the processor is further configured to: generateinstructions to perform peer-to-peer communication with a firstneighboring wireless device of the one or more neighboring wirelessdevices after discovering the first neighboring wireless device using areceived discovery signal.
 10. The apparatus of claim 8, wherein theprocessor is further configured to: generate instructions to nottransmit the discovery request signal in response to determiningmovement less than the threshold amount since the transmission of theprior discovery request signal.
 11. The apparatus of claim 8, whereinthe discovery request channel occurs in a first sub-frame of a discoveryresource set.
 12. The apparatus of claim 8, wherein the discoveryrequest channel is assigned by a base station.
 13. The apparatus ofclaim 8, wherein the processor is further configured to: monitor one ormore discovery request channels in a discovery resource set.
 14. Theapparatus of claim 13, wherein the discovery resource set is assigned bya base station.
 15. An apparatus, comprising: a memory; and a processorin communication with the memory, wherein the processor is configuredto: generate instructions to monitor one or more discovery requestchannels in a discovery resource set; and generate instructions totransmit a discovery signal on a discovery channel in the discoveryresource set, wherein the instructions are generated in response to oneof: determining that a relevant discovery request signal has beenreceived from a neighboring wireless device; and determining movementgreater than a threshold distance since transmission of the priordiscovery request signal, wherein the threshold distance comprises aspecified distance since transmission of a prior discovery requestsignal.
 16. The apparatus of claim 15, wherein the processor is furtherconfigured to: generate instructions to perform peer-to-peercommunication with the neighboring wireless device based, at least inpart, on the received relevant discovery request signal.
 17. Theapparatus of claim 15, wherein the processor is further configured to:generate instructions to not transmit the discovery request signal inresponse to determining movement less than the threshold amount sincethe transmission of the prior discovery request signal.
 18. Theapparatus of claim 15, wherein the discovery request channel occurs in afirst sub-frame of a discovery resource set.
 19. The apparatus of claim15, wherein the discovery request channel is assigned by a base station.20. The apparatus of claim 15, wherein the discovery resource set isassigned by a base station.